Gas burner and mixing tube construction



April 26, 1949. N. E. HILL ETAL GAS BURNER AND MIXING TUBE CONSTRUCTION INVENToRs Patented Apr. 26, 1949 GAS BURNER AND MIXING TUBE CONSTRUCTION Napoleon E. Hill and om J. Ress, Milwaukee,

Wis., assignors to L. J. Mueller Furnace Company Application April 4, 194s, serial No. 659,628

(cl. 15s-99) Claims.

This invention relates to improvements in gas burner and mixing tube constructions.

' A general object of the invention is to provide an improved gas burner and mixing tube so constructed as to eliminate extinction noise and flashback characteristics.

In connection with the operation of gas burners having conventional mixing tubes associated therewith, considerable dimculty has been experienced when burning gas with high ignition velocity characteristics. A very pronounced objection has been the extinction noise and flashback characteristics common to the operation of gas burners formedA with conventional mixing tubes. It is the theory that in such structures the extinction noise and "ashback characteristics are caused by the following conditions: When the supply of gas to the burner is shut oil', there is, of course, residual gas in the piping between the shut-off valve and the burner ports or orifices. Upon the closing of the gas supply shutoff valve, the quantity of gas within the device and reaching the burner ports is gradually reduced. Consequently, there is less energy in the gas streams leaving the burner ports and the quantity of primary air within the mechanism is consequently reduced. However, the ratio of primary air to gas greatly increases. Up to a denite ratio of primary air to gas, the ignition velocity of the combustible mixture increases and a situation attains wherein after the gas supply shut-off valve to the mixing tube is closed, the ignition velocity increases until it is greater than the velocity of the primary air-gas mixture in the burner ports. At such time the i'lame will travel back or recede through the burner ports into the burner head and will ignite the primary airgas mixture therein. If there is a sufficient volume of the combustible mixture within the mechanism, an explosion or extinction noise results.

With the foregoing explanation in mind, the present invention aims at eliminating objectionable explosions and extinction noises inherent to the operation of conventional gas burner mechanisms by providing a gas burner and mixing tube construction wherein the mixing tube communicating with the burner head takes the form of an upwardly projecting elbow or trap having a substantial conduit portion thereof above the level of the burner ports. Inasmuch as the air-gas mixture within the burner head has a specic gravity less than that of air, with the improved upwardly extending trap-like construction of the mixing tube, after the gas supply valve has been shut off, the air-gas mixture in the burner head tends to rise to the highest point in the trap-like portion of the mixing tube. Such trapped air-gas mixture within the elevated portion of the mixing tube then tends to block or counteract the normal i'iow of air admitted through the air valve in the mixing tube, and by blocking the flow of additional air, the flashback or extinction noise tendency of the burner is overcome.

A more specic object of the invention is to provide a gas burner and mixing tube construction wherein the mixing tube is in the form of an upwardly projecting trap and having located therein at a common point the air and gas inlets.

A further object ofthe invention is to provide a gas burner and mixing tube construction wherein the mixing tube has a portion of substantial length at an elevation above the elevation of the burner gas ports to receive a light air-gas mixtui-e, with such portion of the mixing tube being interposed between the air and gas inlets and the burner ports.

A further object of the invention is to provide a gas burner and mixing tube construction of such a formation that the primary air and/or the primary air-gas mixture must travel upwardly and then downwardly before reaching the burner head with the uppermost point of flow being substantially above the plane of the burner ports.

A further object of the invention is to provide a gas burner and mixing tube construction which is very simple, is easy to install, service and regulate, is relatively inexpensive, and is well adapted for the purposes described.

With the above and other objects in view, the invention consists of the improved gas burner and mixing tube construction and its parts and combinations as set forth in the claims, and all equivalents thereof.

In the accompanying drawing ln which the same reference characters indicate the same parts in all of the views:

Fig. 1 is a. longitudinal vertical sectional view of the improved gas burner and mixing tubeconstruction with an outer end portion of the burner head being broken away;

Fig. 2 is a plan view of the showing in Fig. 1;

Fig. 3 is a sectional view taken -on line 3-3 of Fig. 1, and

Fig. 4 is an enlarged fragmentary longitudinal sectional view of a gas burner and mixingtube construction illustrating a slight modification of the invention. f

Referring now more particularly to the drawing, it will be observed that a hollow burner is indicated generally by the numeral 8. In. a top amasar burner head there are a plurality of burner port stools 9 with drilled gas ports or orices I0 therethrough. The particular type of gas port referred to is merely by way of illustration and the burner head may, within the purport of the invention, be formed with any conventional type of gas port. The inner end of the burner head 8 is curved upwardly and the gas entrance II therein is surrounded by an annular shoulder I2 adapted to have seated thereon the adjacent end of a mixing tube, indicated generally by the numeral I3. The end portion of themixing tube I3 referred to, is securely connected to the shoulder I I of the burner head and is provided with any suitable form of gas tight joint.

'I'he mixing tube I3 is in the form of an elbow or trap having a Vertical portionextending substantially upwardly from the burner head at an elevation considerably above the plane of the burner gas ports I0. The mixing tube I3 is then curved downwardly, and in the form of the invention disclosed in Figs. 1, 2 and 3 its outer end terminates in a ared portion I having an opening therein in a horizontal plane above the plane of the gas burner ports I Il. Within said ared end of the mixing tube are spaced webs I5 adapted to cooperate with an air shutter I5 and which carry a central boss I1 having secured through the opening therein a gas orifice nipple I8 whose threaded depending extremity receives the end of a gas supply pipe I9: The adjustable air shutter I6 may be movably associated with the flared end of the mixing tube I3 in any desired manner, and one convenient mode of connection is that illustrated wherein the shutter I6 is adjustably threaded onto the threaded inner end of the gasA supply pipe I 9 whereby it may be turned into and out of selected proximity to the open end of the mixing tube and the webs I5 therein.

In the form of mixing tube illustrated in Figs. 1, 2 and 3, it is apparent that the outer end of the mixing tube terminates in a horizontal plane slightly above the plane of the gas ports I0 in the burner head and said end of the mixing tube forms a common inlet for primary air and gas. The air-gas mixture is caused to flow rst upwardly in the elbow-like mixing tube I3 and then downwardly to the burner head and longitudinally through the interior of the burner head, being exhausted through the gas ports I 0 where ignition takes place.

If, as is conventional in the operation of a gas burner, an automatic .shut-off valve (not shown) terminates gas ow from the gas supply pipe I9 into the mixing tube I3, a condition exists where only primary air enters the mixing tube and thus dilutes the air-gas mixture within the apparatus. For a, time this residual combustible fluid mixture within the system will iiow to and through vthe burner ports I 0 but eventually a condition will attain wherein the ignition velocity is greater than the velocity of the air-gas mixture in the burner ports. The tendency would then be for the flame to travel back into the burner head and ignite the primary air-gas mixture therein, resulting in a "ashback or extinction noise. By Virtue of the improved mixing tube I3 in association with the burner head 8, lthis contingency is prevented because the airgas mixture in the burner head is lighter than air and consequently flows back in the burner head and rises in the upright portion of the mixing tube I3, the latter having an elevation in excess of that of the burner ports. 'I'his light 4 air-gas mixture, extending up to the highest point of the mixing tube I 3, and being interposed between the primary air inlet end I4 of the mixing tube and the gas orices I0 blocks the normal ow of primary air admitted into the mixing tube.

A slight modification of the invention is illustrated in Fig. 4 wherein the downturned outer extent of the mixing tube I3' terminates in a ilared portion I4' which is below the level of the gas ports III in the burner head. In this modification the flared portion I4' of the mixing tube carries a gas orifice nipple I8 with attached gas inlet pipe I9 and air shutter IB' in the same irlnanner as in the principal form of the invenion.

In both forms of the invention the primary air inlet and the gas inlet or supply are common to the outer extremity of the mixing tube and at a level considerably below the peak of the mixing tube. Consequently, the mixing tube is designed to establish therein, under certain conditions, a column of air-gas mixture interposed between the primary air and gas inlets and the burner ports.

From the foregoing description, it will appear that the improved gas burner and mixing tube construction is simple and novel and is well adapted for the purposes described.

What is claimed as the invention is:

l. In'a gas burner construction, a hollow elongated. burner head formed with burner ports in the top portion thereof, a mixing tube connected to the burner head at substantially a right angle to the axial line of the burner head and having first and second vertical legs joined by a bight portion, said mixing tube legs extending substantially above the plane of the burner ports, the lower end of said second leg of the mixing tube having a fluid outlet in communication with the interior of the burner head below said bight portion, and means entering a. lower portion of the first leg of the mixing tube substantially below said .bight portion for admitting primary air and gas whereby the gas-air mixture must iiow into said first leg portion and then downwardly through said second leg portion of the mixing tube at right angles to the axial line of the burner head before entering the latter.

2. In a gas burner construction, a hollow elongated horizontally disposed burner head formed with burner ports in its top portion, a vertically directed elbow-shaped mixing tube having first and second vertical legs joined by a bight portion, said mixing tube legs extending substantially above the plane of the burner ports, the lower end of said second leg having a fiuid outlet in communication with the interior of the burner head below said bight portion, and means for admitting primary air and gas into a lower portion of the rst leg of the mixing tube substantially below said bight portion in a direction parallel to the direction of air and gas flow through the burner ports.

3. In a gas burner construction, a hollow elongated horizontally dlsposed burner head formed with burner ports in its top portion, a vertically directed elbow-shaped mixing tube projecting substantially above the plane of the burner ports and having first and second vertical legs joined by a bight portion, the lower end of said second leg having a uid connection with the interior of the burner head below said bight portion, substantial extents of the first and second legs of' the mixing tube having their axial lines extending vertically a substantial distance above the plane of the burner ports, and means entering the lower extremity of the rst leg of the mixing tube substantially below said bight portion for admitting primary air and gas. l

4. In a gas burner construction, a hollow elongated horizontally disposed burner head formed with burner ports in its top portion, a vertically directed elbow-shaped mixing tube having rst and second vertical legs joined by a bight portion with said mixing tube legs extending substantially above the plane of the burner ports, the lower end of said second leg substantially below said bight portion being connected to the burner head and in communication with the in'- terior thereof, and means for admitting primary air and gas into said rst leg of the mixing tube substantially below said bight portion but at an elevation substantially above the plane of the burner ports and in a direction parallel with flow through said burner ports.

5. In a gas burner construction, a hollow elongated horizontally disposed burner head formed with burner ports in its top portion, a vertically directed elbow-shaped mixing tube having rst and second vertical legs joined by a bight portion with said mixing tube legs extending sub- 6 stantially above the plane of the burner ports.

. the lower end of the second leg of the mixing tube, substantially below the bight portion, be-

ling connected to the burner head and in communication with the interior thereof, and means for admitting primary air and gas into a lower portion of the first leg of the mixing tube below said bight portion and at an elevation substantially below the plane of the burner ports and in a .direction parallel with iiow through the burner ports.

' NAPOLEON E. HILL.

OTTO J. RESS.

REFERENCES CITED The following references are` of record in the le of this patent:

UNITED STATES PATENTS 

